As disclosed in the co-filed application referred to above, which application is incorporated herein by reference, the most relevant prior art is believed to be the formation of lithium aluminates or halolithium aluminates for recovery of Li.sup.+ from aqueous solutions and the use of cation exchange resin for removing Li.sup.+ from aqueous solutions.
In the said co-filed application one method contemplated for preparing the anion exchange resin containing the microcrystalline LiX.multidot.2Al(OH).sub.3 is to impregnate the resin with AlCl.sub.3, then use ammonia to change the AlCl.sub.3 to Al(OH).sub.3, then add a lithium halide to form a lithium aluminate, and then heat to form the microcrystalline LiX.multidot.2Al(OH).sub.3, where X is a halogen, dispersed or suspended within the resin. The resin thus prepared is relatively long-lived and may be employed numerous times in a two-stage cyclic process where Li.sup.+ values are recovered from brine in one step and the Li.sup.+ values are eluted from the resin in another step by using an aqueous wash, preferably a weak solution of lithium halide. Even though the two-steps may be repeated, sequentially, numerous times, the resin capacity is likely to decrease eventually or accidentally to the point at which regeneration or rejuvenation is desirable.
The present invention improves on the preparation, properties, and the performance of the resin/LiX.multidot.2Al(OH).sub.3 composition referred to above by employing aq. lithium hydroxide to form a microcrystalline LiOH.multidot.2Al(OH).sub.3 structure which is then reacted with a halogen acid or halide salt to obtain the LiX.multidot.2Al(OH).sub.3. Throughout this disclosure, the symbol X is used to denote a halide, with chlorine being the preferred halide. The term "microcrystalline" is used to indicate small crystals (formed in the small pores, voids, and spaces in the resin) which are detectable by X-ray diffraction, if not by a microscope.